As a conventional technology, a rotation angle detector for detecting a direction of a rotating magnetic field has been proposed (e.g., see JP 2007-10449 A).
A rotation angle detector disclosed in JP 2007-10449 A or JP 2016-514833 A has a sensor disposed with a pair of magnetic detection elements in a plurality of directions with respect to a rotating magnetic field, and a signal processing part that processes a signal output from each magnetic detection element of the sensor and outputs a signal corresponding to an angle of the magnetic field. In the rotation angle detector the signal processing part specifies an influence of magnetic noise by comparing a phase and an amplitude of each output of the pair of magnetic detection elements when the magnetic field is rotated, and outputs a signal with reduced influence of magnetic noise by subtracting the influence of the magnetic noise, or by performing calculation processing such as averaging individual outputs of the pair of magnetic detection elements.
In the rotation angle detector of JP 2007-10449 A or JP 2016-514833, however, although the magnetic noise influence is reduced and the rotating magnetic field direction is detected, a rotational centre of the rotating magnetic field needs to substantially coincide with a centre of the rotation angle detector. Therefore, in case a plurality of rotation angle detectors is disposed (for example, a pair of rotation angle detectors for preventing a malfunction or for backup at a time of failure) and a centre of one rotation angle detector is made to coincide with the centre of the rotating magnetic field, a centre of another rotation angle detector does not coincide. Further, if the middle of the centres of both the rotation angle detectors is made to be the rotating magnetic field centre, no centre of the rotation angle detectors coincides. As a result, the problem occurs that the magnetic field detected by the rotation angle detector does not provide ideal change of magnetic field in design and that rotation cannot be detected. Further it may be necessary to correct a relationship between at least the magnetic field to be detected and an output signal. Moreover, for one rotation angle detector the magnetic detection element needs to be arranged in a plurality of directions with respect to the rotating magnetic field, causing the problem that the sensor shape cannot be made smaller than at least a region where the magnetic detection elements are disposed.
Hence, there is a need for a rotation angle detector wherein at least one of these drawbacks is avoided or overcome.